Edelbrock 455 Olds Dyno Mule - Rocket Booster

Run for cover, it's a Rocket attack! Thundering from concrete bunkers across the nation and raining down upon unsuspecting Ford, Mopar, and yes, even Chevy racers, the Oldsmobile V-8 is poised for a comeback that's guaranteed to recall the virtues of big cubic inches, low peak engine speed, and mountainous torque.

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The force behind the rocket renaissance is the recently introduced #6051 Performer RPM aluminum cylinder head from Edelbrock. We have to give the people at Edelbrock a great big pat on the back for having the guts to design, tool, and manufacture exotic heads for the not-so-mainstream Olds big-block. But hey, this is the same outfit that recently introduced light-alloy castings for underdog motors such as the Ford FE and the Pontiac V-8 (our spooks tell us that owners of other overlooked V-8s will be happily surprised in the near future).

Rigorous testing prior to introduction is essential to get the best results. To that end, Edelbrock put together a 455 Olds dyno mule motor to flog these new castings in search of the balance between reliability and performance. Instead of a one-off titanium billet monument to exclusivity, the dyno mule is made of common parts that work well.

Cylinder Heads
When Edelbrock senior design engineer Danny Castillo initiated work on the Olds cylinder head project two years ago, he wanted the final result to outperform the vaunted cast-iron factory W-30 head by a wide margin. He consulted the Wernher Von Braun of Olds Rocket motors, Joe Mondello, to learn which areas needed improvement. The most obvious change was the switch to 356 T6 aluminum from cast iron, saving 25 pounds per head. Helicoil inserts in the threaded exhaust header/exhaust manifold mounting holes ensure a long service life. And hardened ductile-iron valve seats and long-wearing phosphor-bronze valve guides provide worry-free street operation on unleaded pump gasoline.

Increased power is the direct result of maximized cylinder pressure. The stock Olds head is secured to the block by 10 shared head bolts, four around each cylinder. Although some engine designs incorporate more head bolts-and theoretically have better head gasket clamping-the Olds doesn't suffer a reputation for blowing head gaskets. But just to make sure modern builders who take expectations beyond the stratosphere with nitrous oxide or supercharging don't get into trouble, the deck surfaces of the heads are 5/8 inch thick to resist the flexing that tends to make head gaskets go pop. While the heads accommodate stock 7/16-inch fasteners, the periphery of each head bolt hole is counterbored to 1/2 inch to provide a piloting reference for those who want to use larger studs for even more reliability when the compression ratio exceeds 11.5:1.

As you might expect, large W-30-size 2.07-inch intake and 1.68-inch exhaust valves are employed for better breathing. These valves are bigger than non-W-30 valves, and they're made from high-quality stainless steel with hardened tips for maximum street and strip durability. The intake-valve stems are 0.089 inch longer than the W-30, while the exhaust stems gained 0.113 inch to accommodate an installed-valvespring height greater than stock. Thus, cams with up to 0.600-inch lift can be used without fear of coil-bind. (The maximum lift afforded by stock-length valves is 0.500 inch.)

4/12Smaller-than-stock exhaust ports actually improve flow numbers over those of even the best factory performance head. Here, a header gasket with stock-size port openings is compared with an Edelbrock exhaust port. This mismatch with headers or exhaust manifolds does not affect performance.

The rocker arm attachment points also received upgrades. While stock Oldsmobile heads utilize a pedestal mount and stamped-steel rocker arms, the Edelbrock heads accept a stud-and-guideplate arrangement that is much more stable in a high-stress environment. The 7/16-inch studs are paired with Helicoils to eliminate pull-out problems with stiff valvesprings. This reconfiguration requires custom rocker arms and hardened pushrods, which are readily available from Mondello Performance Products.

One of the Edelbrock design team's primary objectives was to appeal to as wide a market segment as possible. For street-oriented folk who will gladly do a weekend cylinder-head swap but draw the line at having to change pistons too, the Edelbrock aluminum heads are a direct replacement for cast-iron stockers. Their 77cc combustion chambers almost match the 79-80cc chambers in the non-W-30 production big-block 400, 425, and 455 heads (the extremely scarce '68-'69 W-30 heads had 72 cc's), so a swap to Edelbrock castings won't change the compression ratio by a significant amount. The ambitious engine builder will revel in the extra-thick deck surfaces, which can be milled significantly without sacrificing strength to yield compression ratios in excess of 13:1. As for small-block owners-260, 307, 330, 350, 403-some restrictions apply. (Check out the "Will They Fit My 403?" sidebar above.)

As the brainstorming between Castillo and Mondello progressed, the shortcomings of the production Oldsmobile ports became apparent. The duo increased intake port volume from 177cc to 188cc and reshaped and opened up the throats to achieve airflow numbers of 272 cfm, versus the maximum of 204 cfm common to the W-30 production head. On the exhaust side, Mondello revealed that although the stock Olds ports look quite capable, a depression on the port floor hurts flow. When reworking iron heads for maximum performance, he routinely fills this depression, but since the Edelbrock effort was a start-from-scratch proposition, Castillo raised the floor of the exhaust port to eliminate the problem. The stock W-30 head shows 162 cfm, while the Edelbrock #6051 flows an impressive 207 cfm. And for those who must have more, there's plenty of beef left over for additional porting work. Despite the improvements, all the intake and exhaust manifold fastener locations are identical to those on stock ports.

Dyno Mule Details
The best cylinder heads on earth are useless without a strong short-block to support them. Fortunately, a mild reworking of some stock Olds components is all it takes to do the job. The Edelbrock mule is based on a '70 455 block bored 0.030 oversize. The cast crank prepped by Castillo Crankshaft Service in Santa Fe Springs, California, includes a 0.010/0.010 undercut, polished journals, and chamfered oil holes for better bearing lubrication. That this motor was subjected to dozens of full-throttle dyno pulls with the stock forged rods is testimony to the strength of the OEM components. To ready them for their task, the rod beams were polished, shot-peened to remove stress risers, and fitted with quality ARP 3/8-inch fasteners. Automotive Balancing (Southgate, California) did all the work on the connecting rods and balanced the reciprocating assembly.

The beautiful thing about the big Oldsmobile is that it needn't operate at extreme rpm to deliver the goods. In the world of Olds drag motors, anyone spinning his Rocket beyond 6,500 rpm is considered a sadist. Sure enough, this big-butt mule registered 449.4 hp at a lazy 5,000 rpm and 542 lb-ft of torque at a mere 4,000 rpm on 92 octane unleaded. Via their dished tops, the forged Federal-Mogul pistons (PN L2323) produce a street-friendly 9.5:1 compression ratio, and the stock press-fit pins have proven totally reliable on the dyno.

It appears as if Oldsmobile enthusiasts everywhere have been dealt a winning hand. Finally, a vengeance weapon in the war against the in-crowd. And if you're tired of seeing rats and Mice swapped into your favorite Olds musclecars, then maybe the day of the anti-swap has arrived. Go ahead: Drop an Edelbrock-fortified Rocket into a Camaro (403 Trans Am mounts), Nova (V-8 Omega mounts), or Chevelle (V-8 Cutlass mounts). Kick butt and then watch the fireworks when you pop the hood.

Will They Fit My 403?
It seems ironic that during the late '70s more 403 Oldsmobile motors were installed in Pontiac Firebirds than in Olds 442s, but it's true. Between 1977 and 1979, 279,026 Trans Ams rolled off the assembly line, a large percentage of which used corporate "6.6 Litre" 403 power instead of the more likely "T/A 6.6" Pontiac 400 motor. With a stock output of 185 net horsepower, the L80 Olds 403 four-barrel was no ball of fire. Now, the #6051 Edelbrock Performer RPM Oldsmobile cylinder head can give those anemic old birds new wings. But there are a few details to attend to.

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First, the 403 is based on a block with a 9.330-inch deck height (as are the 260, 307, 330, and 350 engines). The 400, 425, and 455 engines use a taller block with a 10.625-inch deck height-hence the "big-block," "small-block" terminology. The Edelbrock Olds head doesn't care what engine it goes on, but because the small-block is narrower than the big-block, the 403 must use a small-block intake manifold. The best choice is the dual-plane #7111 Edelbrock Performer RPM Olds 350. Additional material around the port runner openings allows them to be enlarged to match the port dimensions of the new heads. This step is essential for maximum power output. Mondello stocks these manifolds-with the port enlargement work completed-as PN 7111-455.

Secondly, as children of the smog '70s, all 403 four-barrel powerplants were built for low-octane unleaded gas. Mondello tells us their deeply dished pistons and 83cc combustion chambers yield a static compression ratio of 8:1, despite the factory rating of 8.5:1. Thus, a pair of Edelbrock heads, with their 77cc chambers, on your Olds 403-powered Trans Am would effectively raise the compression ratio to a "whopping" 8.5:1. While the superior ports would enhance performance, the lack of compression would most certainly dull the edge. For full advantage on a 403, the Edelbrock heads must be milled to reduce chamber volume, or the pistons must have less dish area.-SM

12/12For the latest in Rocket science, pick up a copy of Joe Mondello's Oldsmobile V-8 Engine Technical Reference Manual. It's filled with vital information on blueprint specifications, obscure but critical production variations, and tips on building for reliability and performance. Mondello can also supply a multitude of specialty Olds hard parts that will further enhance the Edelbrock heads.